"I washed all my clothes."
I don't think 全部洋服を洗濯しました is correct. 全部 is a word indicating the amount like 一枚、二枚、少し or 半分, so it most naturally goes before the verb, or you can use の between the amount and the noun, if you want to put the amount to the beginning. I don't know why, but すべての洋服 sounds better to me than 全部の洋服.
The issue I had was the "correct" answer provided after I got it wrong included the character "の" in it despite there not being any "の" available to select. Very frustrating that you then need to hunt down an alternative sentence structure to the "correct" one provided.